New Findings On Ancient Greenhouse Climate Suggest Higher Co2 Levels

Using a paleo-CO2 proxy based on leaf gas-exchange principles (the Franks model), the authors studied two species of the fossil plant Pseudotorellia from three samples at the Tevshiin Govi lignite mine in Mongolia. Their findings showed median CO2 concentrations of 2132, 2405, and 2770 ppm. Earlier reliable CO2 estimates were under 1400 ppm; the newer high values, though accompanied by large uncertainties due to low stomatal density in the leaves, align better with the current understanding of Earth's long-term climate sensitivity. The study suggests an Earth-system sensitivity of 3–5°C per CO2 doubling, closer to modern estimates. It also highlights the need for careful scrutiny of inferred inputs in paleo-CO2 estimates, as these contribute significantly to overall uncertainty. These new insights could reshape our understanding of ancient climate dynamics and improve future climate projections. Co-authors include scientists from the Mongolian Academy of Sciences, Chinese Academy of Sciences, and Research Associates Pat Herendeen (Chicago Botanic Garden) and Peter Crane (Oak Spring Garden Foundation).
July 26. 2024